1. Field of the Invention
The present invention relates to a three-dimensional image display apparatus. In particular, the present invention relates to a stereoscopic image display apparatus of a projection type which can display a stereoscopic image using a single display device by double-scanning a pair of images photographed by a pair of video cameras, respectively, and synthesizing the double-scanned images by line interlacing to form the stereoscopic image.
2. Description of the Prior Art
Humans perceive a stereoscopic effect because different images are formed on the retina of each eye due to the distance between the eyes (about 2.5 inches). The difference between the images generated on each retina is caused by the horizontal distance of the image as projected on each retina. Parallax, on the other hand, is caused by the horizontal distance between two points of an image as projected on a two dimensional monitor. Parallax can be used to generate the appearance of the stereoscopic effect.
There has been long and steady research in developing a display which causes the viewer to perceive a stereoscopic image. One well known technique is the xe2x80x9cboth-eyexe2x80x9d type stereoscopic image realization which is achieved by utilizing spectacles worn by the viewer.
Generally, red-blue color type spectacles, polarization spectacles, and electronic shutter type spectacles are commonly used for viewing the stereoscopic image. According to the red-blue color type technique, a red-colored image (R) filtered from a left-side image and a blue-colored image (B+G) filtered from a right-side image are synthesized with a positive or negative parallax, and the synthesized image signal is displayed. Using the color spectacles, the viewer can perceive a stereoscopic image by having the viewer""s left eye observe only the red-colored image through a red color filter, while the viewer""s right eye observe only the blue-colored image through a blue color filter. On the other hand, a stereoscopic image in motion can be generated by an analog type stereoscopic system in which the stereoscopic image is filmed using two cameras and is then displayed using two projectors.
According to a liquid crystal shutter type stereoscopic system, the screen is divided into odd lines and even lines. A left-side image is provided for the odd lines and a right-side image is provided for the even lines. The images are synthesized to create a stereoscopic image, and the synthesized stereoscopic image is displayed on a monitor. The viewer perceives the stereoscopic image by observing the left-side image only by the left eye, while the right shutter of the spectacles is shut, and observing the right-side image only by the right eye, while the left shutter is shut. The operation of the shutters is synchronized with the image displayed on the monitor.
According to a conventional stereoscopic image display apparatus for displaying a stereoscopic image on a display screen as shown in FIG. 1, a pair of image signals are generated by two video cameras 12 and 14 located at a predetermined distance from an object 10 at predetermined separation therebetween. The pair of image signals are then displayed on a single display screen 20 by two display devices 16 and 18, respectively, overlapping each other.
Such stereoscopic display apparatuses are disclosed in Japanese Patent Laid-open No. Pyung 5-336550 and U.S. Pat. No. 5,260,773. Japanese patent Laid-open No. Pyung 5-336550 discloses a stereoscopic display technique whereby two pairs of image signals are interlaced for each line in a vertical direction for each pair of the image signals to be synthesized, the synthesized pair of image signals are formed and then displayed on a single display screen by two projectors, respectively, U.S. Pat. No. 5,260,773 discloses another stereoscopic display technique whereby a pair of image signals are synthesized by field interlacing and the synthesized image signal is transmitted. Upon reception, the transmitted image signal is separated into a pair of image signals, and the pair of image signals are displayed by two display devices, respectively.
However, such conventional stereoscopic image display apparatuses have drawbacks in that they require two separate projectors in order that two images, i.e., the left and right images, be separately displayed on a single display screen, overlapping each other. This causes an increase in the size of the stereoscopic image display device and complicates its mechanical structure.
It is an object of the present invention to solve the problems involved in the prior art, and to provide a stereoscopic image display apparatus having simplified mechanical structure and reduced size by displaying a stereoscopic image using a single projector. The image can then be viewed using conventional spectacles such as the ones disclosed in, for example, U.S. Pat. No. 5,260,773.
In one aspect of the present invention, two separate cameras are used to picture an object and generate a first and a second television signals corresponding to the left and right images. A receiver receives the television signals and reproduces the left and right image signals, respectively. A double-scanning section scans the left and right image signals with a doubled horizontal frequency, and produces a left and a right double-scanned image signals. A multiplexing section alternately selects the left and right double-scanned image signals at a switching speed of the doubled horizontal frequency, and produces a single multiplexed double-scanned image signal. A projection type display projects the multiplexed double-scanned image signal onto a single display screen.
In another aspect of the present invention, the left and right image signals of the two cameras are scanned by the double-scanning section at a doubled horizontal frequency, to produce left and right double-scanned image signals. A multiplexing section alternately selects the left and right double-scanned image signals at a switching speed of the doubled horizontal frequency, and produces a single multiplexed double-scanned image signal. A transmitter is used for transmitting the multiplexed double-scanned image signal as a television signal. A receiver is used for receiving the television signal and providing a demodulated multiplexed double-scanned image signal. A projection type display projects the demodulated multiplexed double-scanned image signal onto a single display screen.
In still another aspect of the present invention, the left and right image signals are scanned by the double-scanning section to produce left and right double-scanned image signals. A multiplexing section alternately selects the left and right double-scanned image signals at a switching speed of the doubled horizontal frequency, and produces a single multiplexed double-scanned image signal. A projection type display projects the multiplexed double-scanned image signal onto a single display screen.